This is an indication that the incoming video is probably not timed correctly. This is unfortunately common on PCs with on-board video – sometimes installing the correct video drivers (instead of using what Windows ships with) will fix the problem. The DSE24 only supports the exact SMPTE timings – which some video sources fail to produce. Most modern video cards (both ATI- and NVidia-based) produce proper timings just fine; if a PC doesn’t produce correct timings with its current video card, a video upgrade card will usually make it work. Laptops are a somewhat more tricky situation, since adding video cards to them can be hard/impossible; Try upgrading the drivers on that machine and this may fix the issue. To be clear, the DSE24 supports resolutions of: 1920×1080@30, 1280×720@60, 720×480@60, and 640×480@60. These should be supported video modes on most modern machines.